Generally, the control mechanism and the operation of an electric vehicle rely on a power system. The power system comprises a motor, a motor controller, a motor driver and batteries. During the operation of the power system, heat energy (or waste heat) is generated and thus the temperature of the power system increases. The elevated temperature deteriorates the performance of the power system and reduces the use life of the power system. For cooling the power system of the electric vehicle, the electric vehicle is usually equipped with a radiator. Moreover, a cooling liquid is circulated between the power system and the radiator. Consequently, the heat from the operating power system is transferred to the cooling liquid and dissipated to the air through the radiator.
However, the cooling performance of the radiator is obviously affected by the ambient temperature. For example, as the ambient temperature increases (e.g., higher than 35 degrees Celsius), the temperature of the cooling liquid within the radiator also increases. In case that the operating power of the power system is higher, the output temperature of the cooling liquid is possibly in the range between 50 and 60 degrees Celsius after the cooling liquid passes through the power system and the temperature of the cooling liquid is reduced by the radiator. The temperature of the cooling liquid is higher than the ideal operating temperature of the power system (e.g., in the range between 5 and 40 degrees Celsius). Under this circumstance, the temperature of the power system cannot be reduced to the ideal operating temperature after the power system is cooled by the circulation of the cooling liquid of the radiator. Consequently, the performance of the internal components of the power system is possibly degraded, the output of the power system becomes unstable, and the use life of the power system is shortened. Moreover, the temperature of the power system affects the performance of the electric vehicle. For example, the electric vehicle has the optimized performance when the temperature of the power system is in the range between 5 and 40 degrees Celsius. As known, the thermal control system of the existing electric vehicle cannot be operated in both of an extreme cold condition and an extreme hot condition (e.g., in the range from minus 40 degrees Celsius and 40 degrees Celsius). That is, it is difficult for the thermal control system of the existing electric vehicle to be operated in both of the extreme cold condition and the extreme hot condition to effectively dissipate the heat of the power system and maintain the normal operation and desired performance of the power system (e.g., a motor). Generally, additional heating and cooling mechanisms can overcome the above drawbacks. However, the fabricating cost of the electric vehicle is largely increased. Therefore, there is a need of providing a cost-effective thermal control system for effectively maintaining the ideal operating temperature of the cooling liquid when the electric vehicle is operated various ambient temperatures.
Moreover, the heated airflow from the air-conditioning system of the electric vehicle is produced by converting electric energy into heat energy. When the electric vehicle is driven in an extreme cold weather, the air-conditioning system of the electric vehicle consumes much electric energy. In comparison with the conventional vehicle, the electric vehicle is more power-consuming while driving in the extreme cold weather. Moreover, after the electric vehicle is charged, the mileage reduction becomes obvious. Therefore, there is a need of providing a method and a thermal control system for efficiently increasing the energy utilization efficiency of the heated airflow when the electric vehicle is driven in the extreme cold weather.